What? This already exists and most ISPs already does it, bcp38.
They're only validating that the traffic that they originate use the IP addresses that they manage. So ISP that has an interface with 100.0.0.1/24 make sure that any ingress on that interface has source IP addresses in that range. If everyone does this spoofing becomes impossible and there's no cooperation or whatever you described required.
They're only validating that the traffic that they originate use the IP addresses that they manage. So ISP that has an interface with 100.0.0.1/24 make sure that any ingress on that interface has source IP addresses in that range. If everyone does this spoofing becomes impossible and there's no cooperation or whatever you described required.